(a) Field of the Invention
This invention relates to solid transparent fragrance-emitting articles. The articles can be three dimensional self-supporting figures formed by rotational, solid or shell molding techniques.
(b) State of the Art
Transparent or clear fragrance-emitting articles are aesthetically more appealing than those which are opaque.
In general, fragrance loss during processing has been a problem in manufacture of solid transparent fragrance-emitting articles and has limited the means by which such articles can be formed. Also, rotational and shell molding techniques which entail substantial processing periods have generally been unsatisfactory for use in manufacture of fragrance emitting articles due to loss of fragrance oils by vaporization particularly when using polymers having high set temperatures. Polymer materials, which have higher temperature set points necessitating higher processing temperatures, are particularly unsuitable as base materials for fragrance-emitting articles, since fragrance loss increases with increased temperature.
U.S. Pat. No. 3,926,655 describes clear cosolvent free polyamide resin articles containing up to 30% perfume oil. Solid objects are made by melting resins having a molecular weight of 6000 to 9000, adding perfume and rapidly cooling, as by quenching in cold water. The product can be molded under heat and pressure to the desired shape. The patent recomends use of closed, pressure vessels during mixing to avoid loss of fragrance oil by vaporization. When the final objects are injection molded (which is effected at high temperatures), it is preferred that the fragrance oil be introduced directly into the resin feed.
Other polymeric materials are unsuitable for use in fragrance-emitting articles because of problems with exudation of cosolvents for the fragrance and polymer or of other materials present in the article. U.S. Pat. No. 4,110,261 refers to a prior art polyamide resin for use in fragrance emitting objects having good gloss and transparency characteristics, but which becomes tacky to touch upon aging. U.S. Pat. No. 3,819,342 describes transparent candles formed from certain thermoplastic polyamide resins and a flammable solvent selected from the group consisting of saturated and unsaturated fatty alcohols, unsaturated fatty acids, esters of fatty acids with polyhydric alcohols and glycerol and mixtures thereof. The solvent is present in an amount sufficient to gel the resin. The candles may also include a fragrance which is emitted upon burning. Mineral oil may be used as an antiflaring agent. These compositions generally produce a relatively soft product which requires a support vessel and which is subject to syneresis.
U.S. Pat. No. 4,051,159 describes shaped, self-supporting transparent fragrance emitting articles formed from polyamide resin having a molecular weight of 2,000 to 10,000, a C.sub.14 to C.sub.22 alkyl alcohol as solvent and a fragrance emitting material. The polyamide may be formed from C.sub.16 to C.sub.22 linear fatty acids, such as linoleic acid and a di- /or polyamine, such as diethylene triamine and ethylene diamine. According to the patent, the materials are blended at 150.degree. to 200.degree. F. Optionally up to 15% mineral oil may be added to the composition to facilitate production of a homogenous mixture.
The present invention provides a composition, the set point of which is relatively low, resulting in reduced fragrance loss, thus permitting manufacture of three dimensional figures by rotational or shell molding. The plasticizer/solvent system of the composition imparts improved long-range stability to the fragranced products. The fragrance-emitting articles of the invention are stable during storage and use and do not suffer from syneresis, tackiness, softening or loss of shape.